EP0112452A2

EP0112452A2 - Catalytic preparation of nitroalkanes from alkanols

Info

Publication number: EP0112452A2
Application number: EP83110434A
Authority: EP
Inventors: William Verne Hayes
Original assignee: Dow Chemical Co
Current assignee: Dow Chemical Co
Priority date: 1982-12-01
Filing date: 1983-10-19
Publication date: 1984-07-04
Also published as: NO158095C; CA1203814A; EP0112452A3; EP0112452B1; US4431842A; AU561023B2; DK156389C; DK496183D0; ZA835805B; DK496183A; NO158095B; ES524883A0; BR8304730A; DE3374931D1; DK156389B; JPS59110654A; AU1767783A; ES8505638A1; NO833130L

Abstract

@ A process of making nitroalkanes which comprises reacting a lower alkanol, e.g. methanol, and nitric acid (HNO<sub>3</sub>) in the vapor phase in the presence of a catalyst which is an oxide or a salt of a metal of Group II of the periodic table, e.g. calcium chloride.

Description

Nitroalkanes are an essential stabilizing ingredient employed in 1,1,1-trichloroethane when it is used in vapor degreasing and cold cleaning. All manufacturers throughout the world add nitromethane and/or nitroethane to their commercial 1,1,1-trichloroethane- based solvents. Normally nitro-alkanes are manufactured by a vapor phase nitration of the alkane with either nitric acid or N0₂. There is a mixture of products formed due to carbon-carbon scission. Thus, for example, when propane is nitrated, the products include 1-nitropropane, 2-nitropropane, nitroethane and nitromethane. Because of the oxidative conditions other oxygen containing compounds are also produced, e.g. aldehydes, acids and carbon oxides. Patents disclosing such a process are U.S. 2,844,634 and 2,905,724.
Improvements in these vapor phase nitrations are claimed by employing the nitric acid or nitrogen oxides together with oxygenated sulfur compounds, e.g. S0₂, H₂SO₄, (U.S. 3,272,874) and by conducting the nitration in the presence of ozone (U.S. 3,113,975).
Other processes involve nitration of alkanes by nitrogen peroxide (N0₂)₂ in the presence of oxygen (air) under pressure at 150°-330°C (U.S. 3,780,115); reacting an alkene with nitric acid in the presence of a lower aliphatic monocarboxylic acid anhydride to produce a nitroester, subsequently reducing it with an alkali borohydride to form the nitroalkane (U.S. 3,706,808) and reacting organic amines with ozone (U.S. 3,377,387).
The present invention is a departure from known methods in that it employs the reaction of an alkanol with nitric acid, or N0₂ gas, in the vapor phase over a catalyst.
The catalyst is a salt or an oxide of a Group II metal, e.g. calcium or barium chloride, which may be supported or pelleted.
The process for manufacturing lower nitroalkanes, especially those containing 1-3 carbon atoms, according to the present invention involves a vaporization of a lower alkanol and nitric acid, mixing their vapors and passing over a catalyst which is a salt or oxide of a metal from Group II of the periodic table. The alkanol and nitric acid are conveniently pumped as liquids to individual vaporizers, mixed, and fed to a fixed bed catalyst over which they are transformed into nitromethane. An inert gas, e.g. nitrogen, is preferably used as a diluent, and can be recycled.
The vapors of the alkanol and nitric acid are thoroughly mixed, desirably in proportion of 10 to 1 noles of alkanol per mole of HN0₃, preferably 4 to 2, and this mixture is preferably diluted with an inert gas, e.g. nitrogen, desirably at 2 to 15 moles of the inert iiluent per mole of alkanol. The preferred range is from about 4 to about 10 moles of diluent per mole of alkanol reactant. The diluent may be selected from inert gases including nitrogen, argon, the carbon oxides, steam and nixtures thereof.
The gas mixture is preferably preheated to a temperature of from 100 to 250°C and the catalyst bed is preferably maintained at a temperature within the range of 150 to 350°C, more preferably from 210 to 260°C.
The catalyst is a compound of metals of Group II of the periodic table, preferably magnesium, calcium, strontium and barium. Salts of these metals, including the chlorides, sulfates, and nitrates may be employed. The oxides of these metals are also useful as catalysts for the reaction. They may be employed separately or in combination. A preferred combination is CaCl₂/BaCl₂ in a molar ratio of 1/4 to 4/1.
Either the oxides or salts may be burdened on an inert support and used in this manner. Methods of making supported catalysts are well known to the art. For example, the support may be impregnated by immersing it in a salt solution or by spraying the solution onto the support. A slurry is used in the case of oxides or insoluble salts.
Pressures employed in the process are desirably from 1 to 150 psig (6.9 to 7130 kPa gauge) and preferably from 6 to 50 psig (41.4 to 345 kPa gauge).

Representative Preparation of Catalyst

A catalyst was made for use in the following Examples by immersing an alumina support (a low surface area (<1 m²/g) spherical support of medium porosity manufactured by Norton and designated SA-5205) in an amount of aqueous CaCl₂ solution sufficient to completely wet it. Excess water was evaporated and the catalyst dried. The amount of CaCl₂ supplied was sufficient to provide a 21 percent by weight loading on the support. Portions were calcined under a nitrogen purge (oxygen excluded) at 150°C, 415°C, 500°C, 600°C, and 700°C each for a period of 4 hours.

Example 1

The different portions of the above prepared catalysts were run in a 4 foot by 3/4 inch (1220 mm by 19 mm) stainless steel tubular reactor system equipped with fluidized sand heat control, pressure and flow controllers, chilled water scrubber column, and an alarm system. A Brooks thermal mass controller was used to meter nitrogen flow. Milton Roy positive displacement pumps were used to meter the methanol and nitric acid flows. Methanol conversion differed only slightly, varying from 13 percent to 22 percent for the reaction run at 245°C, 5.5 sec contact time with a MeOH/HN0_3/N₂ ratio of 4/1/24. Selectivity varied considerably for the reaction under the above conditions as is shown below in tabular form.
Thus, the preferred method of preparing the catalyst is to calcine the salt or oxide of the metal on a support for a period of 2 to 10 hours at a temperature of from 500° to 700°C.

Example 2

A quantity (370 ml.) of a catalyst prepared according to the above description, calcined at 700°C for 4 hours and consisting of a 1/1 (atomic ratio of Ca/Ba) mixture of calcium chloride and barium chloride coated at 17.6 percent by weight on a low surface area alumina support (SA-5205) was loaded into the 4-foot (1220 mm) stainless steel tube reactor described above and heated to 270°C with a diluent gas (nitrogen) purging through the system. The pressure was controlled at 7 psig, preheater temperature 185°C, nitrogen flow 4000 cc/min., then nitric acid was started at 0.0076 gram mole/min. rate. Methanol was then started at 0.0301 gram mole/min. rate (4/1/24 CH₃OH/HNO₃/N₂ mole ratio).
Analysis of the condensed reactor effluent showed a 17 percent conversion of methanol and a 60 percent selectivity to nitromethane.

Examples 3-7

A supported catalyst containing CaCl_2/Ca0 (1/1 mole ratio) was employed at different reactant ratios, contact times and temperatures to obtain the conversions and selectivities shown in Table I. The support was the same as employed in Examples 1 and 2 above and catalyst loading was 19.7 percent based on weight of the finished catalyst.

Examples 8-14

In other experiments anhydrous CaCl₂ pellets (5 mesh) were used with conditions and results shown in Table II.

Examples 15-21

Other Group II metals were tested in a 1-foot by 1 inch (305 mm x 25.4 mm) stainless steel tubular reactor equipped as the longer reactor. Conditions under which the reaction was run were preheater temperature 185°C, nitrogen flow 4000 ml/min. and pressure 7 psig. Table III shows the reaction parameters and results:

Example 22

A catalyst of 16 percent CaCl₂ on alumina spheres, calcined at 700°C for 4 hours, employed in the 4-foot (1220 mm) reactor at various temperatures, was run at a MeOH/HN0_3/N₂ ratio of 3.8/1/24, 4 sec. contact time and a pressure of 8 psig. A quantity of 370 ml of catalyst was employed as in Example 1. Results are shown in Table IV.

Claims

1. A process for making nitroalkanes by reacting in the vapor phase a mixture of a lower alkanol and nitric acid or nitrogen dioxide, the improvement of which comprises the reaction in the presence of a catalyst which is an oxide or a salt of at least one metal of Group II of the periodic table.

2. The process of Claim 1 wherein the catalyst is an oxide or salt of calcium, barium, strontium or magnesium.

3. The process of Claim 2 wherein an inert diluent gas is employed and the reactant and diluent gases are preheated.

4. The process of Claim 3 wherein the gases are preheated to a temperature of from 100 to 250°C and the reaction temperature is from 150 to 350°C.

5. The process of Claim 4 wherein the molar ratio of lower alkanol to nitric acid is from 10/1 to 1/1.

6. The process of Claim 5 wherein the inert diluent gas is present in an amount of from 2 to 15 moles based on moles of alkanol present.

7. The process of Claim 1 wherein the catalyst is an oxide or salt of calcium and barium in combination.

8. The process of Claim 1 wherein the lower alkanol contains 1-3 carbons.

9. The process of Claim 8 wherein the lower alkanol is methanol or ethanol.

10. The process of Claim 9 wherein the inert diluent gas is nitrogen, argon, CO, C0₂, steam or mixtures thereof.

11. The process of Claim 10 wherein the temperature of reaction is from 210 to 260°C.

12. The process of Claim 11 wherein the catalyst has been prepared by calcining at a temperature of from 500 to 700°C for a period of 2 to 10 hours.

13. The process of Claim 7 wherein the molar ratio of calcium chloride to barium chloride is from 1/4 to 4/1.